Hey all, the company I work at bought the "Network Cache" system

I absolutley hate the freaking thing. whenever I make changes to an outside file specifically image files, or .swf files... the network cache pulls from it's stored files, and displays the old ones!!! I can never tell if an update has happened, I usually end up calling my wife at home and asking her to look at the page and tell me if it looks different.

Is there some way in the head tags I can make it so that it will expire all the images and .swf files so that it always reloads them?